hum... where did you read that rouges can only win against lower lvl characters? thats what confusing ME
a good played rouge can kill every other class.. some easier, some harder (like priests with shield+fear etc). its all about your equipment and your own skill in playing your class. and of course the skill of your opponent ^^. i wont say im a really good pvper, but i was able to kill some shamans that were red colored for me (one was ?? too) because they really sucked in playing their class.
about the druid.. hm well as i said.. when u play ur character good u have less problems in pvp.. in my opinion a druid isnt that weak as most ppl say. hes a caster, healer, tanker, stealther etc. the point that he can do so much things is his strength, but the strongest thing that makes a character more powerful in some ways than other classes are the healing abilities.. if you cant stop a class from healing you will die a slow and annoying death
thats why i fear priests more than every shaman ^^
hope that helped you a bit. i love my rouge and have much fun with him